The effectiveness of the inverted ILM flap method is crucial in the treatment of macular hole (MH), particularly those larger than 400 microns, as larger MHs present a more challenging surgical task. Large MHs are more likely to experience failure of closure or reopening after initially being successfully closed, compared to small MHs [13]. A recent meta-analysis has indicated that the inverted ILM flap technique may offer benefits over regular ILM peeling, especially in terms of achieving higher closure rates (RR 1.10, 95% CI 1.02 to 1.18; p = 0.01) for large MH [14]. The challenge in this approach lies in ensuring that the inverted ILM flap remains in place while performing the subsequent fluid-gas exchange manipulation.

According to reports, 14% of cases experience spontaneous retroversion of the free end of the ILM flap during the fluid-air exchange, which may result in surgical failure [8]. To improve the approach, we use a small amount of VISCOAT to surround the MH and cover the inverted ILM flap. This serves a dual purpose: acting as an adhesive and providing weight to maintain the flap during the fluid-gas exchange. Additionally, we administer VISCOAT into both the MH and the area above the MH that is symmetrical to the mirror image before injecting the ICG solution. This is done to minimize the potential toxicity of the ICG [15]. VISCOAT may be left in place without causing any harm to the retina. Consequently, in our cases, we did not observe any dislodged inverted ILM flaps during or after the surgery. Furthermore, the surgical closure rate for MHs was 98% in our study. MHs measuring less than 400 μm achieved 100% closure, whereas MHs ranging from 400 to 800 μm attained a closure rate of 98%. Very large MHs, exceeding 800 μm, achieved a closure rate of 91.3% in our case series. This closure rate, particularly for MH larger than 400 μm, is significantly higher than previously reported rates [16]. We believe that the modification of the viscoelastic-assisted inverted ILM (VILM) flap technique contributed to our high success rate, which is further supported by having a larger series of patients and by categorizing the study patients according to different sizes of MH.

The use of inverted flap procedures, including both temporal [10] and superior [17, 18] ILM flaps, has been shown to result in superior anatomical and functional recoveries compared to the traditional method of ILM peeling. Gliosis can occur as a result of ILM peeling, which involves Müller cell fragments. The gliosis may manifest on the surface of the ILM and within the retina when a section of the peeled ILM remains attached to the MH. Consequently, the ILM could potentially serve as a scaffold to promote tissue proliferation [19]. An Italian study involving 27 eyes with MH (> 400 μm) further compared the outcomes of the inverted ILM flap technique, with a single-layer ILM inverted over the MH, and a multiple layer ILM folded within the MH [20]. Both groups achieved a high anatomical success rate and significant visual improvement, except in the case of exceptionally large MHs (> 700 um), which closed more efficiently (0/2 vs. 2/2 cases) when employing the multilayer ILM. The primary distinction in our study lies in the use of a substantial single-layer inverted ILM flap to fill the MH, yielding promising clinical outcomes. Utilizing a bundle of multilayer ILM can be beneficial for facilitating anatomical restoration by effectively sealing and bridging the hole. Nevertheless, the inverted ILM acts as a framework for the rapid growth of glial cells within the MH [19], creating a conducive environment for photoreceptors to migrate closer to the fovea. Excessive insertion of ILM may lead to excessive fibrosis in the central macula, potentially hindering subsequent functional recovery. Our approach involved partially removing the inferior ILM in a half-circular manner to create a flap approximately the size of one disk diameter. This flap was then flipped to cover the MH from its upper edge, considering the force of gravity. As a result, the MH was treated by applying a large single-layer inverted ILM flap. We hypothesize that the presence of a single-layer ILM over the MH may facilitate a more organized and natural structure for the growth of glial cells, aiding in the closure of the MH without excessive fibrous tissue formation in the fovea.

Our cases demonstrated that 86.5% of the eyes showed a noticeable improvement in BCVA at 3 months and 6 months postoperatively. This finding aligns with a meta-analysis that concluded the inverted ILM flap technique is more effective than traditional ILM peeling in achieving better visual outcomes at three or more months after surgery for large MHs [14]. However, some meta-analyses have reported no difference in visual outcomes between the inverted ILM flap technique and traditional ILM peeling groups at 6-month follow-up, despite observing higher closure rates in the inverted ILM flap technique [21, 22]. The variation in results may be attributed to the relationship between baseline visual acuity (VA), the type of MH closure, and the final visual outcome. We found a correlation between BCVA improvement and baseline VA (r = 0.76, p = 0.03). Additionally, an impressive 91% of our patients with Type 1 closure exhibited a foveal configuration resembling either a U-shape or V-shape, resulting in a significant improvement in vision. Conversely, patients with Type 2 closure–characterized by the absence of the retinal pigment epithelium, photoreceptors, and external limiting membrane in the central area as observed through OCT–experienced poor visual outcomes during the follow-up period.

Several novel surgical techniques have been developed to address challenging MHs, such as the inverted ILM flap combined with an autologous blood clot technique, the neurosensory retinal flap, the perfluorocarbon liquid-assisted inverted ILM flap technique, the ILM transposition and tuck technique, and the use of a human amniotic membrane plug [16]. We utilized vitrectomy in combination with the VILM flap approach for treating MHs.

In conclusion, our case series demonstrated that the VILM flap technique is a significant surgical method with favorable success rates in treating large MHs [23]. Appropriate use of VISCOAT can effectively prevent dislocation or backward rotation of the ILM flap during fluid-gas exchange and mitigate the toxic effects of ICG staining on the retinal pigment epithelium. Implementing this procedure has the potential to enhance the success rate of the original operation while optimizing both the morphological and functional outcomes. We strongly endorse this straightforward and cost-effective technique for repairing macular holes.